Herbs, terrestrial, autotrophic or rarely heteromycotrophic. Pseudobulbs subterranean or borne above ground, cormlike, tuberous, or rhizomatous, usually several noded, with several slender or thick fibrous roots at base. Leaves appearing at or after anthesis, 1 to many, basal, base tapering or contracted into a long petiole-like stalk, reduced to scales in heteromycotrophic species; petiole-like leaf base sometimes overlapping and forming a pseudostem. Inflorescence erect, lateral, racemose or rarely paniculate, laxly to subdensely many flowered or occasionally reduced to a solitary flower. Flowers resupinate, small to large, sometimes showy; pedicel and ovary slender. Sepals free, similar; lateral sepals usually slightly oblique, sometimes adnate to column foot. Petals similar to dorsal sepal or slightly wider; lip ± erect, usually 3-lobed, lateral lobes erect and embracing column, rarely entire, base usually spurred or saccate; disk usually with a callus consisting of lamellae, ridges, or fringes. Column short to long, usually winged; column foot present or less commonly absent; anther terminal, incompletely 2-locular, anther cap often with 2 projections; pollinia 2, ± cleft, waxy, attached to a suborbicular viscidium by a short, broad stipe.

About 200 species: tropical and subtropical regions, most diverse in Africa, but also widespread from Madagascar and the Mascarene Islands to C and tropical Asia, the SW Pacific islands, and N and NW Australia; 13 species (two endemic) in China.